This application is a continuation of application Ser. No. 08/288.845, filed Aug. 11, 1994 now abandoned.
This invention pertains to wood pulp bleaching processes, such as those which Employ gaseous bleaching reagents contacted with high consistency (i.e. twenty percent or more) fluffed pulp, and in particular to a means for gas-sealingly conveying shredded pulp, in a pulp-handling process, to a downstream vessel or device.
Wood pulp bleaching with gaseous reagents, such as ozone and other high reaction rate gases, promises significant reduction of objectionable pulp mill effluents to streams and other bodies of water, as well as reduction of objectionable gaseous emissions. Elimination of chlorine compounds from the bleaching sequence promises great economic and ecological benefits. However, incorporation of these bleaching reagents can impose significant capital costs on the pulp mill due to the use of pulp transport devices which are expensive and generally require frequent maintenance.
In the use of a bed type reactor, for example, such as described in U.S. Pat. No. 3,814,664, issued to Carlsmith, et al, a thick stock pump is required to feed the pulp to the fluffer while sealing the vessel pressure from the thickening device which generally operates under atmospheric pressure. In another method, described in U.S. Pat. Nos. 5,181,989; 5,164,043; and 5,164,044 issued to Griggs, et al, and U.S. Pat. Nos. 5,174,861; 5,211,811; and 5,188,708 issued to White, et al, a screw feeding device is used to transport the pulp to the fluffer, again while sealing the vessel pressure from the thickening device which operates under atmospheric pressure.